Grinding apparatus for fibrous materials



June v1959 A. J. A. AS'PLUND 2,391,733

GRINDING APPARATUS FOR FIBROUS MATERIALS Filed July 15, 1954 3 Sheets-Sheet 1 INVENTOR. z' /or/AM AgT/UQ ASPLIJND BY m2 June 23, 1959 A. J. A. ASPLUND 2,891,733

- GRINDING APPARATUS FOR FIBROUS MATERIALS Filed July'15. 1954 3 Sheets-Sheet a Am/E/o/MA/ 4187904 4SPA u vD United States Pate 2,891,733 Patented June 23, 1959 GRINDING APPARATUS FOR FIBROUS MATERIALS Arne Johan Arthur Asplund, Bromma, Sweden, assignor to Aktiebolaget Defibrator, Stockholm, Sweden, a corporation of Sweden Application July 15, 1954, Serial No. 443,638 Claims priority, application Sweden July 15, 1953 1 Claim. (Cl. 241-256) This invention relates to grinding apparatus for the disintegration or breaking down of certain material, preferably of the kind composed of or containing fibres. The apparatus is of the type comprising a rotatable and a non-rotative or stationary grinding member, such as in the form of grinding discs enclosed within a casing. The rotatable grinding member is carried by a shaft mounted in a supporting frame and is axially displaceable to provide adjustment of the mutual spacing between the grinding members and of the compressive pressure exerted upon the material introduced between said members. The apparatus is primarily intended to be used for defibrating of wood chips in a steam atmosphere under high pressure to cause the fibres to become separated from one another. The fibrous material is then, possibly after a subsequent grinding operation, utilized for the manufacture of paper, pasteboard, fibre boards and similar products.

The degree of disintegration of the wood chips which the defibrator is capable of attaining is largely dependent upon the accuracy with which the grinding discs can be adjusted, and during the grinding operation maintained in their position, relatively to one another. For this reason, it is of great importance that first, the working surfaces of the grinding discs are parallel to one another with a minimum of deviation from true parallelism, and second, that the play or clearance between the discs is as small as possible. As the discs have a diameter frequently amounting to one meter and more, it will be readily understood that this accuracy in relation to the positions of the grinding discs places extraordinary de mands on preciseness of construction and the adjustment of the defibrator. The primary object of the invention is to provide a grinding apparatus, and in particular defibrator, satisfying high requirements in these respects.

In a defibrator there prevails a pressure amounting to -15 kgs. per square centimetre and together with the grinding pressure, subjecting the casing enclosing the grinding discs to high stresses. A more specific object of the invention is to provide a housing which withstands such stresses yet nevertheless permits easy replacement of the grinding discs and their adjustment, assuring the securement of the desired play or clearance between the grinding surfaces. A still further object of the invention is to provide a strong and stable connection between the housing and the support, said connection maintaining the play or clearance substantially free from stresses in the defibrator such as are caused by the grinding and steam pressures. A further more particular object of the invention in this respect is to attain such accuracy regarding the adjustment and maintenance during operation of the play or clearance that the defibrator at the same time serves as a finishing-machine, i.e. the separation of the fibres from one another and even the disintegration of the fibres themselves is advanced to such an extent as to frequently render a subsequent treatment in the finishing machine unnecessary.

The invention will be hereinafter described more detailed with reference to an embodiment illustrated by way of example in the accompanying drawings, features characteristic of the invention also being set out in this connection.

Fig. 1 is a side elevational view of a grinding apparatus constructed in accordance with the invention;

Fig. 2 is a top plan view of the same; and

Figs. 3 and 4 placed end-to-end constitute a vertical longitudinal section through the apparatus.

Referring to the drawings, 10 designates the frame of the apparatus carrying a shaft 12 mounted in two bearings respectively generally denoted by 14 and 16. On one of its ends the shaft is connected by means of a coupling 18 with the shaft of a driving motor 20. On its opposite end the shaft 12 carries a grinding disc 22. The shaft 12 and the grinding disc 22 are adjustable in an axial direction relatively to a stationary grinding disc 24. For this purpose a coupling sleeve 26 is secured to the shaft 12 and engages, by means of ridges 28, axially extending grooves 30 disposed in an external casing 32 enclosing the coupling 18 and connected with the motor shaft.

The bearing 14 located adjacent the coupling is intended to absorb the radial load and is suitably composed of a spherical double-row roller bearing having its inner ring splined onto the shaftl2 by means of a clamping sleeve 34. The outer ring 36 of the bearing is encased by inner bearing housings 38 in the form of a sleeve and provided with a bearing cover 40 fixing the outer ring relatively to said inner housing 38. This latter is in turn disposed axially slidable in an outer bearing housing 42 secured to the frame 10 by means of lateral flanges 44 (Fig. 1). A shoe 46 engages the bearing housing 42 and by a number of pre-compressed springs 43 is kept pressed against the inner bearing housing 38 for the purpose of eliminating any play. The shoe 46 also looks the bearing housing 38 against any movement in a peripheral direction.

The bearing 16 disposed adjacent the grinding disc 22 has conical rollers 51) cooperating with a ring 52 carried by the shaft and with a rotationally stationary ring 54. The bearing 16 is capable of absorbing both axial and radial loads. An annular spacing member 58 is located between the inner ring 52 and a shoulder 56 provided on the shaft 12. The bearing 16 is kept under continuous axial pressure by means of an axial thrust bearing 60 suitably of conical type. The inner ring 62 of said bearing 6&3 is splined onto the shaft 12 through an oil-centrifuging disc 64 by means of a stop nut 66. The outer ring 68 of the bearing 60 is pressed through a pre-compressed conical cup spring 70 and a sleeve 72 against the stationary ring 54 of the bearing 16. The initial axial pressure acting on said bearing corresponds to the pre-cornpression of the spring '78 which may amount to several tons and is at least equal to the axial power component acting on the bearing 16 and produced by the weight of the rotating parts, occurring unbalances inherent to said parts and so forth. In order to be capable of absorbing radial loads, the bearing 16 must at the same time be subjected also to an axial load which latter is insured by the device just described even when the apparatus is out of operation. The sleeve 72 is enclosed within an inner bearing housing '73 in which the bearing ring 54 is disposed and which is axially displaceable together with the shaft 12 in an outer bearing housing 75. In order to eliminate the elfect of play between the two bearing housings 73 and 75, a sliding shoe 74 is disposed to exert a pressure on the bearing housing 73 by means of pre-compressed springs 76. The outer housing 75 as well as the bearing housing 42 are provided at their base with two axially extending sliding rails (not shown) against which the inner bearing housings 73 and 78, respectively, abut.

The rotating grinding disc 22 is rigidly connected to a rotor 73 by means of bolts 80. Within the grinding disc 22, seen in the radial direction, there is located a second grinding disc 82 kept rigidly secured to the rotor '73 by means of bolts 84. The stationary grinding disc 24- is connected with the casing 88 enclosing the grinding discs by means of circumferentially-spaced locking and adjusting devices 86. Each device 86 comprises a fixing bolt 87 engaging the grinding disc 24 with threads and passing with play through a sleeve 89 threaded into the member 88 and having for its object to adjust the position of the grinding disc 24- relatively to said casing. The adjusting sleeve 89 has a polygonal head 91 and is locked by means of a nut 93. The concentric location of the locking and adjusting members relatively to one another avoids bending moments tending to deform the grinding disc 24.

The casing 88 carries within the grinding disc 24, seen in the radial direction, a second stationary grinding disc 90 rigidly connected with said member by means of bolts 92. The surfaces of the two grinding discs 22 and 24, which face one another are channelled in the known manner for the purpose of producing the desired disinte gration of the material to be ground. The discs 82 and 99 may constitute supply members for the material introduced through a channel 94 provided in the casing 83 and preferably also produce a preparatory disintegration of said material.

The casing 88 is sturdily constructed as an oblate spheroid of large dimensions in order to be capable of withstanding the high steam pressure prevailing within it and for avoiding transmitting the grinding pressure to the frame 10. The casing 88 has a strong central part 95 provided with an outlet jacket 96 for the ground fibrous material and on both its lateral walls it is rigidly secured to the frame by means of bolt connections 97. Said bolt connections are disposed symmetrically relatively to a horizontal plane through the centre line of the shaft 12. A stufl'ing box 99 is interposed between the shaft 12 and the casing 88. In accordance with the invention, the casing 88 is horizontally divided in a plane located above the stuffing box 99 and the wall of the supply channel 94. In this way the casing is provided with a top part or cap 161 not participating in the transmission of the grinding pressure from the stationary grinding disc 24 to the frame and detachably connected with the central part of the casing by means of bolts 1113. Upon removal of the top part 1111 the grinding discs are accessible for control and adjustment, an oval opening in the casing permitting removal of the grinding discs for possible replacement becoming uncovered also. The casing 88 is further provided with a prolongation 1G5 projecting upwardly over the plane of division of the casing where it is enclosed by the top part 191 and acts as counter-support for the grinding disc 24. At the base is an opening capable of being closed by a cover lliSa.

The grinding disc 22 is kept under pressure acting in the direction toward the grinding disc 24 by means of a servo-motor generally designated by 98 and comprising a casing 101) rigidly connected with the frame and a piston 1192, both said casing and said piston concentrically and with play surrounding the shaft 12. The piston 102 has a central flange 104 axially displaceable within a chamber 166, the lateral walls 103 and 119 of which limit the path of free motion of the piston in the axial directions. The chamber 106 has at its both ends inlets and outlets 112, 114 for a non-compressive liquid such as oil. The piston 102 is only, with a suitably adjusted small play, sealed against the surrounding casing 1913. Liquid leaking out of the casing is removed through annular grooves 116, 118.

A sleeve 120 provided with external threads may be all) rigidly secured by key 22 1 to the end of the servomotor piston 1412 facing the bearing 16. The thread has a pitch of an order of magnitude of 5 millimetres. The sleeve carries an annular member 122 threaded thereon and provided with an axially-extending groove 124 engaged by a pin 126. The sleeve 121) further carries a ring threaded thereon and an annular plate 128 spaced axially from said ring 136. A number of circumferentially-spaced bolts 132 pass with play through the ring 131.) but are threaded into the plate 128 and a member 13 3 forming a cover sealing the bearing housing 73. The bolts compress springs 136 abutting against the ring 130 which results in eliminating the effect of a play between the threads connecting the members 102 and 134. The member 122 abuts with a spherical face 138 against an annular member 140 provided in the cover 13 1. The total pressure exerted by the springs 136 is larger than the resistance of the parts connected with the shaft 12 when displaced to the left, viewed in the plane or" the Figs. 3 and 4.

A Worm wheel 144 is rigidly secured to the piston 192 of the servo-motor and co-operates with a worm 146 disposed on a transverse shaft 14-3. Said shaft 148 is preferably on its ends provided with a hand wheel 150 and is mounted in bearings 152, 154. By turning the shaft 148 the piston 1132 of the servo-motor is caused to rotate. The housing 73, however, is stationary for which reason the member 122 will be displaced axially and in its movement entrain the housing and also the grinding disc 22 connected with said housing.

The axial movement of the grinding disc 22 relatively to the piston 102 of the servo-motor is controlled by means of a measuring instrument 156 the scale of which is graduated for hundredths of millimetre, for example. and the movable measuring pointer 158 of which abuts against an inclined surface 161) provided on the cover 134. The measuring instrument 156 may be so adjustable that its indicator will assume zero position when the two grinding discs 22, 24 are in conatct with each other. The inclined surface may have an inclination of 30 relatively to the center line of the shaft 12. The pressure fluid, such as oil, is fed into the servomotor 98 from a device generally indicated by 162 and comprising a motor-driven pump, a multiple-way valve and conduits connecting said members with one another and with the servo-motor and a sump. Two such conduits open into the chamber 106 of the servo-motor at 112 and 114, respectively. t is assumed to be suflicient to mention that said device comprises a button 166 for operation of the multiple-way valve.

The desired play or spacing between the grinding faces of the grinding discs 22 and 2 1 when the flange 1114 of the piston of the servo-motor abuts against the surface 111), is adjusted by means of the hand wheel 15 3 while reading off the measuring instrument 156. During such adjustment the piston 102 of the servo-motor is axially stationary, but due to its rotary movement and the connections between it and the housing 134, 73, the bearing 1d. the spacing member 53, the shaft 12, the rotor '78 and the grinding disc 22, these elements will be displaced axially in one or the other direction without said ele ments participating in the rotary movement. in operation of the apparatus, ie when material to be ground is supplied to the grinding discs through the channel 4, pres sure oil is fed into the chamber 1% through the conduit 112. The oil pressure acts on the flange 1114 and is transmitted through the parts 129, 12.2. 14%, 134, '73, 16, 58, '73 and the grinding disc 22 to the material. it will be understood from this explanation that the shaft 12 does not participate in the power transmission from the pressure fluid to the grinding disc 22 but with its short portion located between the shoulder 56 and the rotor.

The grinding pressure is transmitted from the grinding disc 24 to the casing 38 and from said casing through the bolt connections 97 to the frame it) which latter preferably has heavy flanges 168 converging towards one another and thus approaching the shaft 12. All these features assist in minimizing the eifect of occurring heat tensions, the steam pressure and the grinding pressure on the play or clearance between the grinding discs. Due to the bearing devices described above and the radial initial tension pressure acting thereupon, the axial displacements of the shaft 12 are performed without any appreciable disturbance of the centered position thereof which feature also assists in attaining the primary object of the invention of creating and maintaining the required extremely small play between the active faces of the grinding discs in spite of the large diameter of said discs.

If, during the grinding operation, material to be ground agglomerates or hard objects, such as small stones or scrap iron fragments happen to find their way between the active grinding faces, the rotating grinding disc 22 and the power-transmitting members between said grinding disc and the piston 102 of the servo-motor are displaced to the left, viewed in the plane of the Figs. 3 and 4, the flange 104 thereby being caused to disengage the lateral stop surface 110. Said surface constitutes at the same time a stop determining the minimum free play of the disc 22 relatively to the disc 24. By connecting the connection 112 with the sump in the device 162 and instead thereof supplying pressure fluid to the connection 144 the piston 102 of the servo-motor is forced to displace itself to the left and then to entrain all members forming part of the power transmitting chain ending with the grinding disc 22.

Of course, the invention is not limited to the embodiment shown but may be varied in the widest aspects within the scope of the basic idea thereof.

What is claimed is:

In a :defibrator for treating fibrous materials, a stationary grinding disc, a rotatable grinding disc mounted on a horizontally-positioned axle, a frame in which said axle is journalled, a housing arranged around the discs, said housing being constructed in the form of an oblate spheroid with a horizontal axis so as to absorb a high internal pressure, the rotatable grinding disc being axially displaceable and adapted to transfer grinding pressure to the stationary grinding disc and to the housing, the housing having upper and lower parts, the former part being capable of vertical separation along a horizontal plane located well above the axle but with said division plane below the highest positioned parts of both grinding discs, Whereto to provide an access opening to the interior of the housing for the disc, the housing having a prolongation extending upwardly and Within the upper part of the housing, to thereby complete the back support of the stator on the casing.

References Cited in the file of this patent UNITED STATES PATENTS 370,880 Mathiason Oct, 4, 1887 1,412,026 Sturtevant Apr. 4, 1922 2,008,892 Asplund July 23, 1935 2,216,611 Dimm et al. Oct. 1, 1940 FOREIGN PATENTS 285,258 Great Britain Feb. 16, 1928 

